The present invention relates to a plasma processing method and apparatus to be used for the manufacture of semiconductor or other electron devices and micromachines.
In the manufacture of semiconductor or other electron devices and micromachines, thin-film processing techniques using plasma processing have become increasingly important in recent years.
As an example of conventional plasma processing methods, plasma processing using a patch-antenna type plasma source is described below with reference to FIG. 3. Referring to FIG. 3, while the interior of a vacuum vessel 51 is maintained at a specified pressure by introducing a specified gas from a gas supply unit 52 into the vacuum vessel 51 and simultaneously performing exhaustion by a turbo-molecular pump 53 as an exhausting unit, a high-frequency power of 100 MHz is supplied by an antenna use high-frequency power supply 54 to an antenna 55 provided so as to project into the vacuum vessel 51. Then, plasma is generated in the vacuum vessel 51, allowing plasma processing to be carried out with a substrate 57 placed on a substrate electrode 56.
There is also provided a substrate-electrode use high-frequency power supply 58 for supplying high-frequency power to the substrate electrode 56, making it possible to control ion energy that reaches the substrate 57. The high-frequency power supplied to the antenna 45 is fed to a proximity of the center of the antenna 55 via an antenna-use matching circuit 59 by a feed bar 60. A dielectric plate 61 is sandwiched between the antenna 55 and the vacuum vessel 51, and the feed bar 60 serves to connect the antenna 55 and the antenna-use high-frequency power supply 54 to each other via a through hole provided in the dielectric plate 61. Also, the surface of the antenna 55 is covered with an antenna cover 65.
Further, a slit 64 is provided so as to comprise a groove-shaped space between the dielectric plate 61 and a dielectric ring 62 provided at a peripheral portion of the dielectric plate 61, and a groove-shaped space between the antenna 55 and a conductor ring 63 provided at a peripheral portion of the antenna 55.
The turbo-molecular pump 53 and an exhaust port 73 are disposed just under the substrate electrode 56, and a pressure-regulating valve 74 for controlling the vacuum vessel 51 to a specified pressure is an up-and-down valve disposed just under the substrate electrode 56 and just over the turbo-molecular pump 53. The substrate electrode 56 is fixed to the vacuum vessel 51 with four pillars 75.
In the plasma processing described in the prior-art example, however, etching a high melting metal film formed on the substrate 57 would involve deposition of an electrically conductive deposited film on the antenna cover 65, in which case poor close-contactability of the conductive deposited film or occurrence of abnormal discharge at the surface of the antenna cover 65 would make it more likely to occur that the conductive deposited film would be peeled off, falling onto the substrate 57 as dust in some cases. According to a result of the present inventors' experiments, when the substrate 57 coated with a 200 nm thick iridium film was etched to a quantity of 7 pieces, 1000 or more dust particles having 0.23 μm or larger particle diameters were generated on the substrate 57.
Further, in the plasma processing described in the prior-art example, there is another issue that the temperature of the antenna cover 65 increases due to plasma exposure. Since the antenna cover 65 and the antenna 55 are vacuum-insulated from each other, the temperature of the antenna cover 65 gradually increases over repeated plasma processing. According to a result of the present inventors' experiments, it was found that the temperature of the antenna cover 65 increases up to 170° C. after 5-min. plasma processing and 1-min. vacuum holding is repeated six times. Such an abrupt change in the temperature of the antenna cover 65 may cause not only occurrence of dust but also cracks of the antenna cover 65.
In view of these and other prior-art issues, an object of the present invention is to provide a plasma processing method and apparatus which is less susceptible to the occurrence of dust and cracks of the antenna cover.